This proposal for a Clinical Research Center in the Prematurity and Respiratory Outcome Program focuses on selected biological processes that contribute to the pathogenesis of infant chronic lung disease and adverse respiratory outcome. We hypothesize that during early adaptation of the premature lung to air breathing, low content of surfactant protein B and increased levels of inflammatory cytokines in lung fluid reflect the extent of lung immaturity and injury and as such serve as biomarkers for long-term outcome. We further hypothesize that levels of lung nitric oxide production and turnover of elastin serve as biomarkers of lung repair and growth. The objective of Aim 1 is to enroll a cohort of premature infants ^28 wk and collect tracheal aspirate and urine samples for assay of biomarkers as well as data related to their clinical course and respiratory outcome. We will recruit and enroll 160 premature infants at three NICU sites with a history of successful collaboration. Severity of newborn lung disease will be assessed by early and late clinical markers, including requirement for mechanical ventilation at 1 wk and oxygen requirement at 40 wk PMA. We propose a clinical score to quantify lung function during the first year, generated from questionnaires assessing pulmonary symptoms, hospitalizations and medications, and validated by a hypoxic (altitude) challenge test and pulmonary function testing. The objective of Aim 2 is to determine levels of selected candidate biomarkers that are predictive of respiratory outcome at 1 yr. As markers of early lung injury, we will collect tracheal aspirate samples from the subset of intubated premature infants between postnatal d 3- 14 for assessment of surfactant and inflammatory biomarkers. As markers of lung growth and repair, we will utilize noninvasive collections of urine during the evolution of lung disease to evaluate production of nitric oxide/cyclic GMP and turnover of pulmonary elastin. We expect that the biomarker findings, when combined with clinical parameters, will be highly predictive of outcome at 1 y and will provide new information related to the pathogenesis of infant lung disease. The co-PIs are experienced in clinical studies as well as basic and translational research. (End of Abstract) RELEVANCE: This study will provide new information on causes and clinical course of lung disease in premature infants, which is an important public health concern. The findings will suggest new predictors and potential therapies to improve long-term outcome for infants at high risk of lung disease.